As is well known, the game of golf is played with a set of clubs of varying lengths, the longest of these being called "woods" and the relatively shorter clubs being called "irons". As is also well known, a golf club comprises a shaft which has wrapping at one end thereof to form a "grip", the wrapping being leather, a rubber composition, or the like. At the other end of the shaft is attached a so-called "head", which is the striking element when swung into a golf ball.
The shaft may be made of metal (e.g., steel), graphite, glass fiber, or the like. As suggested, supra, the longer clubs of a set generally have heads made of wood and the relatively shorter clubs usually have heads made of iron.
The present invention is directed to club heads known as "woods" and shaped, traditionally, as shown in the drawing of the instant disclosure, FIGS. 1 and 2, reference characters 1 and 3 thereof, respectively. In the interest of clarity, the term "woods" will be employed herein, unless otherwise qualified, to refer generically to "club heads" shaped like those in the aforementioned FIGS. 1 and 2, whether they are made of wood (such as persimmon wood), aluminum, plastic, or other compositions.
In this vein, the present discovery is concerned with polyurethane woods--in other words, golf club heads made entirely or predominantly of a urethane polymer.
As is evident from FIGS. 1 and 2, standard woods have a flat leading ball-striking surface called a "face" 5. See FIG. 2. In FIG. 1 the face is provided with multiple, parallel, horizontal grooves 7. Also, as shown in FIG. 1, the face has a center portion 9 (also known as the "sweetspot"), a left side leading portion 11 known as the "toe" and a right side (rear) portion 13 known as the "heel". The bottom of the wood, the leading edge of which only is shown at 15 in FIG. 2, is called a "sole", and the elongated portion extending from the body (block) of the wood 3 of FIG. 2 to the shaft 17 (cutaway section only shown) is called a "neck" 19. The neck has a hollow center (not shown) into which is fitted shaft 17.
The above-mentioned center portion 9 of the wood face 5 shown in FIG. 1 is delineated laterally by two solid slanted lines 21 forming a keystone or frustoconical configuration, which represents a plate called an "insert" (shown only as delineated by lines 21) fitted into a recessed portion (not shown) in the center of the face of the wood, the insert being fastened to the face by screws 23. Of course, it is imperative that the front surface of the insert, and the toe 11 and heel 13 surfaces, provide, overall, a uniformly smooth club face. This minimizes deflection of the golf ball when other than the sweetspot is contacted by the ball.
The object of the insert is to provide more durability and more distance, the insert being made, in the past, of various materials, including certain metals, ivory, polymers (e.g., phenolics), and the like.
While woods, prior to and since one of golf's immortals, Harry Vardon (1870-1937), have traditionally been made of solid wood blocks, more recent technology has introduced an alternative structure for these blocks which comprises stacked thin wooden sheets firmly laminated by means of interposed thin films of adhesive resins. The resulting stack is then shaped into a wood.
While this alternative has met with significant success, other alternative materials used to make woods have not fared as well, for various reasons. Woods have been made of, for example, aluminum, plastics [acrylonitrile-butadiene-styrene (ABS)], and other metals and polymers. Players using them found the manufacturers' alleged increase in distance questionable; players have complained of an uncomfortable feel at impact and loss of control and accuracy; players reported, for instance, feelings of so-called "shock" at impact and shorter contact (club face/golf ball contact), even for shots perfectly hit; and players were annoyed with vibrations and resultant loss of distance when, at impact, the wood's sweetspot was not met, i.e., when the ball was struck toward or on the toe or the heel of the wood. They often described the just-mentioned difference in control and accuracy between traditional woods and the just-described commercially unsuccessful woods as similar to the difference in feel at impact most players experience between their long irons (1 or 2) and their short irons (6-9). Present-day irons are numbered 1-9, the number 1 iron being the longest and the number 9 iron being the shortest.
As is well known, besides having longer shafts, the long irons have lighter, thinner, and narrower heads than the short irons, and less loft. The longer, less-lofted irons remain in briefer contact with the ball than the more-lofted shorter irons. Short contact times cause increased vibrations; conversely, vibrations diminish as the contact time increases.
The heretofore-mentioned traditional wood and the more recent laminate wood generally have not only an insert of the type discussed supra, and shown in FIG. 1, but, in the interest of durability, a metal sole (bottom) plate, the leading edge only of which is shown at 25 in FIG. 1. Also, various impregnations and coatings are used to protect the wood.
Unfortunately, despite these modifications to the traditional wood block and the laminate woods, the wood is readily damaged. For instance, the face and other surfaces of the wood are quick to bruise and show indentations, and the neck of the wood is prone to crack. A sleeve 27, shown in FIG. 1, usually of plastic material, is conventionally used to cover the mating area of the neck 19 and shaft 17 (as shown in FIG. 2) of the club in order to provide a smooth appearance. This sleeve is likewise prone to cracking.
Even with meticulous craftsmanship and quality control, it is difficult to guarantee reproducibility of a given club head design, including a uniform loft and lie, a uniform club face surface, etc. The art has had to try to master numerous complicated steps (sometimes over 100) to manufacture an acceptable golf club.
Even then, it has yet to overcome severe drawbacks, including club head weight changes due to substantial moisture absorption. Weight changes and the aforedescribed bruises and damages are particularly prevalent problems with fairway woods which are used without tees and subjected to frequent contact with wet grass, roots, or even stones. Generally, the leading edge of the fairway wood is thinner than that of a driver (also called a no. 1 wood) and is more easily damaged, even if the bottom of the wood is protected by a metal sole plate 25 (FIG. 1).
In addition, the above-described elements provided in the sweetspot of the wood face as inserts occasion, particularly when they are fastened by screws, differences in restitution of energy when a golf ball is struck other than directly on the sweetspot. This is why experienced golfers become nostalgic about the earlier no-insert wood face.
From the above commentary, it would seem that, to the experienced player, the optimum in woods would include, inter alia, (i) initial speed and good distance for the golf ball through good restitution of energy, but with minimum shock and vibration, (ii) enhanced control and accuracy monitored by impact feeling, and (iii) durability. Obviously, present-day clubs fail in one or more aspects of these characteristics.
It is a desideratum of the present invention to achieve all of these characteristics, including, in a manufacturing sense, reproducibility of the woods without a multiplicity of steps. As will be seen herein, exceptional goals have been achieved in the present discovery and, surprisingly, without the need for exceptional hardness of materials at point of impact.
A search of relevant art in the U.S. Patent and Trademark Office records revealed the following U.S. patents:
______________________________________ U.S. Pat. No. Date Inventor/s Assignee ______________________________________ 4,068,849 17/I/79 DiSalvo et al. Acushnet 3,979,126 7/IX/76 Dusbiber " 3,966,210 29/VI/76 Rozmus -- 3,937,474 10/II/76 Jepson et al. Acushnet 3,390,881 2/VI/68 Senne Voit ______________________________________
While the first three (3) of the patents are of interest, the Jepson et al. patent is deemed the most pertinent. In this patent a conventional golf club of the type hereinbefore described is shown having an insert ("striking plate") of polyurethane of certain alleged physical and chemical characteristics. See claim 1 of the patent.
As will be obvious, infra, the article of manufacture herein claimed differs materially from that taught by Jepson et al. As a for instance only, the patentees' disclosure is directed exclusively to a polyurethane insert.
Two of the remaining patents uncovered, viz., Dusbiber and DiSalvo et al., are directed to golf balls prepared from, inter alia, diisocyanate monomers. The patent to Rozmus concerns a specially-weighted golf club intended to assist in achieving accuracy. The weights are located in a club head, in each cheek thereof, so to speak, and retained therein with, say, epoxy resin and potting material.
The Senne patent is no more relevant in that it involves, briefly, a wood made, preferably, of a wooden core having a face, the center portion of which is recessed to accept an insert, which core is entirely covered by a polymeric shell, but for the toe and heel of the core. A metal plate is fitted on the polymer-covered sole of the core. Of real interest is the following statement which is in a true sense confirmatory of certain commentary supra: (Senne in col. 2, lines 13-24)
"Solid clubs molded from synthetic resins have been produced commercially, but by preferred standards of golf club performance they have not been satisfactory. Examples of these plastics are nylon, acrylonitrile-butadiene-styrene copolymers and polycarbonates. Because the density of these plastics is greater (by over 100%) than that of wood, it has been necessary to incorporate a central cavity in the solid plastic head. Major disadvantages of this construction are that they do not produce the desired sound on impact, and its dynamic characteristics, particularly in terms of distance, are not so good as those of a conventional wood club."